This invention relates to azeotropes, azeotrope-like compositions, and methods of using azeotropes and azeotrope-like compositions to clean substrates, deposit coatings, transfer thermal energy, lubricate working operations, and aid in foam blowing.
Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrochlorocarbons (HCCs, e.g., 1,1,1-trichloroethane and carbon tetrachloride) have been used in a wide variety of solvent applications such as drying, cleaning (e.g., the removal of flux residues from printed circuit boards), and vapor degreasing. These materials have also been used in refrigeration and heat-transfer processes. While these materials were initially believed to be environmentally benign, they have now been linked to ozone depletion. According to the Montreal Protocol and its attendant amendments, production and use of CFCs must be discontinued (see, e.g., P. S. Zurer, xe2x80x9cLooming Ban on Production of CFCs, Halons Spurs Switch to Substitutes,xe2x80x9d Chemical and Engineering News, page 12, Nov. 15, 1993). The characteristics sought in replacements, in addition to low ozone depletion potential, typically have included boiling point ranges suitable for a variety of solvent cleaning applications, low flammability, and low toxicity. Solvent replacements also should have the ability to dissolve both hydrocarbon-based and fluorocarbon-based soils. Preferably, solvent replacements also have low toxicity, have no flash points (as measured by ASTM D3278-98 e-1, xe2x80x9cFlash Point of Liquids by Small Scale Closed-Cup Apparatusxe2x80x9d otherwise known as SETAFLASH), have acceptable stability, have short atmospheric lifetimes, and have low global warming potentials.
Certain perfluorinated (PFCs) and highly fluorinated hydrofluorocarbon (HFCs) materials have been evaluated as CFC and HCFC replacements in solvent applications. But PFCs and non-flammable HFCs have high global warming potentials. While these materials are generally sufficiently chemically stable, nontoxic, and non-flammable to be used in solvent applications, PFCs tend to persist in the atmosphere, and PFCs and HFCs are generally less effective than CFCs and HCFCs for dissolving or dispersing hydrocarbon materials. Some HFCs are also flammable.
Hydrofluoroethers (HFEs), or highly fluorinated ethers, have also gained interest as replacements for CFCs and HCFCs. HFEs are also chemically stable, have low toxicity, are non-flammable, and are non-ozone depleting. Mixtures of PFCs, HFCs, or HFEs with other organic solvents tend to be better solvents and dispersants for hydrocarbons than PFC, HFCs, or HFEs alone.
Fluorinated ketones are particularly useful as fire extinguishing agents and as a magnesium cover gas. They are cost effective and have a low global warming potential. But they have limited solvent strength.
Many azeotropes possess properties that make them useful solvents. For example, azeotropes have a constant boiling point that avoids boiling temperature drift during processing and use. In addition, when an azeotrope is used as a solvent, the properties of the solvent remain constant because the composition of the solvent does not change during boiling or reflux. Azeotropes that are used as solvents also can be recovered conveniently by distillation.
Thus, there is a need for azeotropes or azeotrope-like compositions that have good solvent strength, low flammability, are non-ozone depleting, and have a relatively short atmospheric lifetime so that they do not significantly contribute to global warming (i.e., low global warming potential).
The present invention provides azeotropes and azeotrope-like compositions of a hydrofluorocarbon and fluorinated ketones. Advantageously, these compositions are non-flammable, have good solvency, are non-ozone depleting, and have a relatively short atmospheric lifetime. Further, they are cost-effective.
In one aspect, the present invention provides azeotropes and azeotrope-like compositions comprising or consisting essentially of a hydrofluorocarbon and a fluorinated ketone. The hydrofluorocarbon is 1,1,1,3,3-pentafluorobutane. The fluorinated ketone is represented by the general formula RfC(O)CF(CF3)2 where Rf is CF3CF2xe2x80x94, CF3CF2CF2xe2x80x94, or (CF3)2CFxe2x80x94.
While the concentrations of the hydrofluorocarbon and the fluorinated ketone included in the azeotrope-like composition may vary somewhat from the concentrations found in the azeotrope formed between them, the boiling points of the azeotrope-like compositions are below the boiling point of the minimum boiling point component. Thus, the azeotrope-like compositions of the present invention include the corresponding azeotrope. Preferably the azeotrope-like compositions are non-flammable.
In another aspect, the present invention provides a method of cleaning objects by contacting the object to be cleaned with one or more of the azeotrope-like compositions of this invention or the vapor of these compositions until undesirable contaminants or soils on the object are dissolved, dispersed, or displaced, and rinsed away.
The present invention also provides coating compositions comprising an azeotrope-like composition and coating material that are useful in the coating process.
In yet another aspect, the present invention provides a method of depositing coating compositions on substrates using the azeotrope-like compositions as solvents or carriers for the coating material. The process comprises the step of applying to at least a portion of at least one surface of a substrate a coating composition comprising: (a) an azeotrope-like composition; and (b) at least one coating material that is soluble or dispersible in the azeotrope-like composition. Preferably, the process further comprises the step of removing the azeotrope-like composition from the coating composition, for example, by evaporation.
The azeotrope-like compositions of the present invention are also useful in fully volatile working fluids. These working fluids act to lubricate the cutting or forming processes used to fabricate metal, cermet, and composite parts and fully evaporate from the surfaces leaving little, if any, residue.
In yet another aspect, the present invention provides a method of transferring thermal energy using the azeotrope-like compositions as heat-transfer fluids.